66 lines
2.0 KiB
C++
66 lines
2.0 KiB
C++
////////////////////////////////////////////////////////////////////////////
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//
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// Copyright 2016 Realm Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or utilied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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////////////////////////////////////////////////////////////////////////////
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#ifndef REALM_OS_ALIGNED_UNION_HPP
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#define REALM_OS_ALIGNED_UNION_HPP
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#include <cstddef>
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#include <initializer_list>
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#include <type_traits>
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namespace realm {
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// Provide our own implementation of max as GCC 4.9's is not marked as constexpr.
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namespace _impl {
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template <typename T>
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static constexpr const T& constexpr_max(const T& a, const T& b)
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{
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return a > b ? a : b;
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}
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template <typename T>
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static constexpr const T& constexpr_max(const T* begin, const T *end)
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{
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return begin + 1 == end ? *begin : constexpr_max(*begin, constexpr_max(begin + 1, end));
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}
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template <typename T>
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static constexpr const T& constexpr_max(std::initializer_list<T> list)
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{
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return constexpr_max(list.begin(), list.end());
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}
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} // namespace _impl
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namespace util {
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// Provide our own implementation of `std::aligned_union` as it is missing from GCC 4.9.
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template <size_t Len, typename... Types>
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struct AlignedUnion
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{
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static constexpr size_t alignment_value = _impl::constexpr_max({alignof(Types)...});
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static constexpr size_t storage_size = _impl::constexpr_max({Len, sizeof(Types)...});
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using type = typename std::aligned_storage<storage_size, alignment_value>::type;
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};
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} // namespace util
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} // namespace realm
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#endif // REALM_OS_ALIGNED_UNION_HPP
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